1. Field of the Invention
The present invention relates to the field of semiconductor wafer processing and, more particularly, to a fluid containment ring used in a processing chamber for disposal of the processing fluid used to deposit and/or remove a material on a semiconductor wafer.
2. Related Applications
The present invention is related to the U.S. Patent Applications entitled "Process Chamber and Method for Depositing and/or Removing Material on a Substrate," Ser. No. 08/916,564, filed Aug. 22, 1997, now U.S. Pat. No. 6,017,437 incorporated herein by reference, and "Multiple Station Processing Chamber and Method for Depositing and/or Removing Material on a Substrate," Ser. No. 09/118,664 filed Jul. 17, 1998, pending.
3. Description of the Related Art
In the manufacture of devices on a semiconductor wafer, it is the practice to fabricate multiple levels of conductive (typically metal) layers above a substrate. The multiple metallization layers are employed in order to accommodate higher densities as device dimensions shrink well below one-micron design rules. Likewise, the size of interconnect structures also need to shrink in order to accommodate the smaller dimensions. Thus, as integrated circuit technology advances into the sub- 0.25 micron range, more advanced metallization techniques are needed to provide improvements over existing methods of practice.
One approach has been to utilize copper as the material for some or all of the metallization of a semiconductor wafer (see for example, "Copper As The Future Interconnection Material;" Pei-Lin Pai et al.; Jun. 12-13, 1989 VMIC Conference; pp. 258-264). Since copper has a better electromigration property and lower resistivity than aluminum, it is a more preferred material for providing metallization on a wafer than aluminum. In addition, copper has improved electrical properties over tungsten, making copper a desirable metal for use as plugs (inter-level interconnect) as well. However, one serious disadvantage of using copper metallization is that it is difficult to deposit/etch. It is also more costly to implement than aluminum. Thus, although enhanced wafer processing techniques are achieved by copper, the potential cost associated with copper processing is a negative factor. Accordingly, it is desirable to implement copper technology, but without the associated increase in the cost of the equipment for copper processing.
In order to fabricate features, circuits, and devices on a substrate, such as a semiconductor wafer, various techniques are known to deposit and etch materials on the wafer. Deposition techniques include processes such as physical vapor deposition (PVD), chemical vapor deposition (CVD), sputtering, and immersion of the wafer in an electrolyte. This last technique can be used for either electroless deposition or for electroplating. In an electroplating technique, the substrate is immersed in an electrolyte (or processing fluid) and positioned in an electric field between a cathode and an anode such that charged particles are deposited onto the surface of the wafer. (See for example, U.S. Pat. No. 5,441,629, which is titled "Apparatus and Method of Electroplating.")
Similarly, a number of techniques are known for removing a material from a wafer. These techniques include reactive ion etching (RIE), plasma etching, chemical-mechanical polishing (CMP), and immersion of the wafer in an electrolyte. Material removal by subjecting an immersed wafer to an electric field employs an equivalent set-up to that used for electroplating, but with an opposite result, since charged particles are removed from the wafer in this instance.
Various processing chambers have been used in which a substrate, such as a semiconductor wafer, is exposed to an electrolyte (or processing fluid) for processing. The chamber has then been emptied through openings along the sides of the chamber and/or through a drain at the base of the chamber. As the electrolyte is drained from the processing chamber, however, the unprocessed side (the back) of the wafer is often exposed to the electrolyte.
The present invention describes a method and apparatus that allows an electrolyte to be drained from the processing chamber into a separate fluid containment ring for storage, disposal, and/or recycling without exposing the back of the wafer to the electrolyte. Thus, the present invention facilitates an efficient use and re-use of the electrolyte through the reduction of the surface area of the wafer exposed to the electrolyte. Further, the present invention allows the separation of the various processing fluids used to process the wafer, which allows separate consecutive processes to be applied within the same process containment chamber. By allowing each processing fluid to be drained from the containment ring of the present invention into a different storage area, the present invention provides an improved control over impurities and particles left within the processing fluid and allows the processing fluids to be more easily filtered and recycled/reused.